Stereo camera with automatic control of interocular distance

ABSTRACT

There is disclosed stereographic camera system including a left and a right camera including respective lenses, plural mechanisms to synchronously set a focal length of the lenses, to synchronously set a focal distance of the lenses, to set a convergence angle between the left and right cameras, and to set an intraocular distance between the left and right cameras. A distance measuring device may be used to measure the distance to an extreme object. A controller may cause an interocular distance and a convergence angle between the left and right cameras to be set based on a maximum allowable disparity, the focal length of the lenses, and a convergence distance.

NOTICE OF COPYRIGHTS AND TRADE DRESS

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. This patent document may showand/or describe matter which is or may become trade dress of the owner.The copyright and trade dress owner has no objection to the facsimilereproduction by anyone of the patent disclosure as it appears in thePatent and Trademark Office patent files or records, but otherwisereserves all copyright and trade dress rights whatsoever.

BACKGROUND

1. Field

This disclosure relates to stereoscopy.

2. Description of the Related Art

Humans view the environment three-dimensionally using binocular vision.Binocular vision is both a visual system and an analytical system. Ourbrain perceives both distance and speed based, in part, on triangulatingvisual light information received by the retinas of our respectivelaterally separated, forward facing eyes. Since both eyes are forwardfacing, the fields of view of each of our eyes overlap, with each eyeperceiving a slightly different perspective of the same area. As wefocus on objects closer to our eyes, our eyes rotate towards each other.As we focus on objects afar, our eyes rotate towards a parallel view.The angle between the lines of sight of each eye is commonly termed theconvergence angle. The convergence angle is higher when we view objectscloser to our eyes and lower when viewing distance object. Theconvergence angle may be essentially zero, indicating essentiallyparallel lines of sight, when we view objects at great distance.

Three dimensional imaging, also known as stereographic imaging, dates atleast as far back as 1838. Historically, stereographic cameras commonlyinclude two lenses spaced laterally apart a similar distance as anaverage human's eyes, approximately 65 mm. The effective distance of thelenses from each other is known as the interocular distance. Theinterocular distance has a strong effect on the apparent depth of astereographic image. Increasing the interocular spacing increases theapparent depth of a stereographic image. Decreasing the interocularspacing has the effect of decreasing the apparent depth of astereographic image.

The presentation of stereoscopic images is commonly achieved byproviding a first image to be seen only by the left eye and a secondimage to be seen only by the right eye. Differences, or disparity,between the two images may provide an illusion of depth. Two imageshaving disparity may be perceived as three-dimensional. Two images, orportions of two images, exhibiting excessive disparity may not beperceived as three-dimensional, but may simply be seen as twooverlapping two-dimensional images. The amount of disparity that aviewer can accommodate, commonly called the disparity limit, variesamong viewers. The disparity limit is also known to vary with imagecontent, such as the size of an object, the proximity of objects withinan image, the color of objects, and the rate of motion of objects withinthe image. The disparity limit, expressed as the angle between the linesof sight of the viewer's eyes, may be about 12-15 minutes of arc fortypical stereoscopic images.

A variety of techniques, including polarization, filters, glasses,projectors, and shutters have been used to restrict each eye to viewingonly the appropriate image.

One approach to displaying stereographic images is to form the left-eyeimage on a viewing screen using light having a first polarization stateand to form the right-eye image on the same viewing screen using lighthaving a second polarization state orthogonal to the first polarizationstate. The images may then be viewed using glasses with polarizinglenses such that the left eye only receives light of the firstpolarization state and the right eye only receives light of a secondpolarization state. Stereoscopic displays of this type typically projectthe two polarized images onto a common projection screen. This techniquehas been used to present 3-D movies.

A second approach to displaying stereographic images is to form theleft-eye and right-eye images alternately on a common viewing screen ata high rate. The images may then be viewed using shutter glasses thatalternately occult either the right or left eye in synchronism with thealternating images.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a stereographic camera in anenvironment.

FIG. 2 is a schematic drawing of a stereographic camera in anenvironment including foreground objects.

FIG. 3 is a representation of images captured by a stereographic camera.

FIG. 4 is a representation of the images of FIG. 2 presented on a commonviewing screen.

FIG. 5 is a block diagram of a stereographic camera system.

FIG. 6 is a block diagram of a computing device.

FIG. 7 is a flow chart of a process for recording stereo images.

Throughout this description, elements appearing in figures are assignedthree-digit reference designators, where the most significant digit isthe figure number and the two least significant digits are specific tothe element. An element that is not described in conjunction with afigure may be presumed to have the same characteristics and function asa previously-described element having a reference designator with thesame least significant digits. Elements that have similar functions foreither the left or right eyes are assigned the same reference designatorwith a suffix of either “L” or “R” to indicate left-eye or right-eye,respectively.

DETAILED DESCRIPTION Description of Apparatus

Referring now to FIG. 1, a stereographic camera 100 may include a leftcamera 110L and a right camera 110R. The term “camera” is intended toinclude any device having an optical system to form an image of anobject and a medium to receive and detect and/or record the image. Theleft and right cameras may be film or digital still image cameras, maybe film or digital motion picture cameras, or may be video cameras. Theleft and right cameras 110L, 110R may be separated by an interoculardistance IOD. Each of the left and right cameras 110L, 110R may includea lens 112L, 112R. The term “lens” is intended to include anyimage-forming optical system and is not limited to combinations oftransparent refractive optical elements. A lens may use refractive,diffractive, and/or reflective optical elements and combinationsthereof. Each lens may have an axis 115L, 115R that defines the centerof the field of view of each camera 110L, 110R.

The cameras 110L, 110R may be disposed such that the axis 115L, 115R areparallel or such that a convergence angle Θ is formed between the twoaxis 115L, 115R. The cameras 110L, 110R may be disposed such that theaxis 115L, 115R cross at a convergence distance CD from the cameras. Theinterocular distance IOD, the convergence distance CD, and theconvergence angle Θ are related by the formulaΘ=2A TAN(IOD/2CD), or  (1)CD=IOD/[2 TAN(Θ/2)].  (2)The interocular distance IOD and the convergence distance CD may bemeasured from a nodal point, which may be the center of an entrancepupil, within each of the lenses 112L, 112R. Since the entrance pupilsmay be positioned close to the front of the lenses 112L, 112R, theinterocular distance IOD and the convergence distance CD may beconveniently measured from the front of the lenses 112L, 112R.

The stereographic camera 100 may be used to form a stereographic imageof a scene 105. As shown in the simplified example of FIG. 1, the scene105 may include a primary subject 130, which is shown, for example, as aperson. The scene 105 may also include other features and objects in thebackground (behind the primary subject). The distance from the cameras110L, 110R to the furthest background object 140, which is shown, forexample, as a tree, may be termed the extreme object distance EOD.

When the images from a stereographic camera, such as the stereographiccamera 100, are displayed on a viewing screen, scene objects at theconvergence distance will appear to be in the plane of the viewingscreen. Scene objects, such as the primary subject 130 in the example ofFIG. 1, located closer to the stereographic camera may appear to be infront of the viewing screen. Scene objects, such as the tree 140,located further from the stereographic camera may appear to be behindthe viewing screen.

Each lens 115L, 115R may have adjustable focus. The stereographic cameramay have a focus adjusting mechanism to synchronously adjust the focusof the two lenses such that both lenses 115L, 115R may be focused at acommon adjustable focus distance FD. The focus adjusting mechanism maycouple the focus of the two lenses 115L, 115R mechanically,electrically, electromechanically, electronically, or by anothercoupling mechanism. The focus distance FD may be adjusted manually, ormay be automatically adjusted. The focus distance FD may be adjustedsuch that the cameras 110L, 110R are focused on the primary subject 130.The focus distance may be automatically adjusted in response to a sensor(not shown) that determines the distance from the cameras 110L, 110R tothe primary subject 130. The sensor to determine the distance from thecameras to the primary subject may be an acoustic range finder, anoptical or laser range finder, or some other distance measuring device.In the case where the cameras 110L, 110R are digital still image, motionpicture, or video cameras, the focus distance may be adjusted inresponse to one or more processors (not shown) that analyze one or bothof the images sensed by the cameras. The processors may be locatedwithin or may be coupled to the cameras.

The convergence distance CD and the focus distance FD may commonly beset to the same distance, which may be the distance from the cameras110L, 110R to the primary subject 130. However, as shown in FIG. 1, theconvergence distance CD and the focus distance FD may not be the samedistance. For example, the focus distance FD may be set at the distancefrom the cameras to the primary subject and the convergence distance CDmay be set slightly longer than the focus distance. In this case, whenthe images are displayed, the primary subject will be seen to be infront of the plane of the viewing screen. The difference between thefocus distance FD and the convergence distance CD may be an adjustableor predetermined offset. The offset may be absolute, in which case theconvergence distance may be calculated by the formulaCD=FD+α  (3)where α is the offset as an absolute dimension. The offset may berelative, in which case the convergence distance may be calculated bythe formulaCD=(FD)(1+β)  (4)where β is the offset as a portion of FD. For example, an absoluteoffset α may be a distance measurement such as one foot or two meters,and a relative offset β may be an expression of a relationship or ratio,such as 5% or 10%. Both the absolute offset and the relative offset maybe zero, in which case CD=FD.

Each lens 115L, 115R may also have zoom capability, which is to say thatthe focal length FL of each lens may be adjusted. The stereographiccamera 100 may have a focal length adjusting mechanism to synchronouslyadjust the focal length of the two lenses such that both lenses 115L,115R may always have precisely the same focal length. The focal lengthadjustment of the two lenses 115L, 115R may be coupled mechanically,electrically, electronically, electromechanically, or by anothercoupling mechanism. Commonly, the focal length of the lenses 115L, 115Rmay be adjusted manually. The focal length of the two lenses 115R, 115Lmay also be adjusted automatically in accordance with a predeterminedscenario.

Referring now to FIG. 2, a stereographic camera 200, which may be thestereographic camera 100, may include a left camera 210L and a rightcamera 210R, each including a respective lens 212L, 212R. The left andright cameras may be film or digital still image cameras, may be motionpicture film cameras, or may be video cameras. The left and rightcameras 210L, 210R may be separated by an interocular distance IOD. Eachlens may have an axis 215L, 215R that defines the center of the field ofview of each camera 210L, 210R. The cameras 210L, 210R may be disposedsuch that the axis 215L, 215R cross at a convergence distance CD fromthe cameras.

The stereographic camera 200 may be used to form a stereographic imageof a scene 205. As shown in the simplified example of FIG. 2, the scene205 may include a primary subject 230, which may be, for example, aperson. The scene 205 may also include other features and objects in theforeground and the background. The distance from the cameras 210L, 210Rto the furthest background object 240, which is shown, for example, as atree, may be termed the maximum object distance MOD. The distance fromthe cameras 210L, 210R to the closest foreground object 245, which isshown, for example, as a plant, may be termed the minimum objectdistance mOD.

Depending on the relationship between MOD, CD, and mOD, the image ofeither the foreground object 245 or the background object 240 may havethe greatest disparity when the scene 205 is presented on astereographic display.

Referring now to FIG. 3, an exemplary image captured by a left camera isillustrated as displayed on a screen 320L and an exemplary imagecaptured by a right camera is illustrated as displayed on a secondscreen 320R. The image displayed on the screen 320L includes an image330L of a primary subject near the center of the display screen, and animage 340L of an extreme background object to the left of the image330L. The image displayed on screen 320R includes an image 330R of theprimary subject near the center of the display screen, and an image 340Rof the extreme background object to the right of the image 330R.

The positional difference, or disparity, between corresponding objectsin the left image 320L and the right image 320R may provide an illusionof depth when the two images are viewed separately by the left and righteyes of an observer. However, to preserve the illusion of depth, themaximum disparity must be less than a limit value which may be bothviewer-dependent and image-dependent. In the example of FIG. 3, thelargest disparity occurs between the images 340L, 340R of the extremebackground object.

Referring now to FIG. 4, the left and right images captured by astereographic camera, such as the stereographic camera 100, may bepresented on a single display screen 420. The image to be seen by theright eye (shown as solid lines) and the image to be seen by the lefteye (shown as dotted lines) may be separated at the viewer's 425 eyesusing polarized glasses, shutter glasses, or some other method aspreviously described. The disparity distance DD between correspondingobjects in the left and right images, such as the images of the tree440L, 440R may be perceived by the viewer 425 as a disparity angle Φ_(D)between the line of sight to the object from the viewer's left and righteyes. The value of the disparity angle Φ_(D) perceived by the viewer 425may be given by the formulaΦ_(D) =A TAN(DD/VD)  (5)where DD is the disparity distance between corresponding objects in theleft and right images and VD is a viewing distance from the viewer 425to the display screen 420.

Since Φ_(D) must be limited to a small angle (such that TANΦ_(D)=Φ_(D)), the maximum allowable disparity distance may be defined asDDmax=Φ_(Dmax)×VD,where Φ_(Dmax) is the maximum allowable angular disparity.

Although the viewing distance VD may not be known at the time astereographic recording is made, the viewing distance VD may be presumedto be, to at least some extent, proportional to the size of the displayscreen 420. For example the Society for Motion Picture and TelevisionEngineers (SMPTE) recommends that, for optimal viewing, the width of ahome theater display should subtend an angle of 30 degrees at theviewer's eyes, corresponding to a viewing distance of 1.87 times thewidth of the display screen. The viewing distance in homes and theatersis commonly greater than the recommended distance, and may range from2.0 to 5.0 times the screen width.

Since the viewing distance VD may be assumed to be a multiple of thescreen width W, the maximum disparity distance between the correspondingimages in a stereographic display may be expressed as a fraction of thedisplay width, as follows

$\begin{matrix}{\frac{{DD}\;\max}{W} = {\Phi_{Dmax} \times K}} & (6)\end{matrix}$where K is the ratio of the viewing distance to the screen width. Forexample, assuming a viewing distance of 2.3 times the screen width, amaximum disparity angle of 15 arc minutes may be converted to a maximumdisparity distance of 1% of the screen width.

Referring now to FIG. 5, a stereographic camera system may include acamera platform 550 coupled to a controller 560. The camera platform 550may include a left camera 510L and a right camera 510R, each of whichhas an associated lens 512L, 512R. The camera platform may include anIOD mechanism 552 to adjust an interocular distance between the leftcamera 510L and the right camera 510R. The camera platform may include aΘ mechanism 554 to adjust a convergence angle between the left camera510L and the right camera 510R. Both the IOD mechanism 552 and the Θmechanism 554 may include one or more movable platforms or stagescoupled to motors or other actuators. The IOD mechanism 552 and the Θmechanism 554 may be adapted to set the interocular distance and theconvergence angle, respectively, in response to data received from thecontroller 560. Within this patent, the term “data” is intended toinclude digital data, commands, instructions, digital signals, analogsignals, optical signals and any other data that may be used tocommunicate the value of a parameter such as interocular distance orconvergence angle.

The camera platform 550 may include a focus mechanism 556 tosynchronously adjust and set the focus distance of the lenses 512L,512R. The focus mechanism 556 may include a mechanical, electronic,electrical, or electro-mechanical linkage between the lenses 512L, 512Rto simultaneously adjust the focus distance of both lenses to the samevalue. The focus mechanism 556 may include a motor or other actuatoradapted to set the focus distance in response to data received from thecontroller 560. The focus mechanism 556 may be manually controlled by anoperator such as a cameraman or assistant cameraman (commonly called a“focus puller”). When manually controlled, the focus mechanism 556 mayinclude an encoder, potentiometer, or other sensor to provide dataindicating the focus distance to the controller 560. The focus mechanism556 may be adapted to operate under manual control and/or in response todata received from the controller 560.

The camera platform 550 may include a zoom mechanism 558 tosynchronously adjust and set the focal length of the lenses 512L, 512R.The zoom mechanism 558 may include a mechanical, electronic, electrical,or electro-mechanical linkage between the lenses 512L, 512R tosimultaneously adjust the focal length of both lenses to the same value.The zoom mechanism 558 may include a motor or other actuator adapted toset the focal length in response to data received from the controller560. The zoom mechanism 558 may be manually controlled by an operatorsuch as a cameraman or assistant cameraman. When manually controlled,the zoom mechanism 558 may include an encoder, potentiometer, or othersensor to provide data indicating the focal length to the controller560. The zoom mechanism 558 may be adapted to operate either undermanual control or in response to data received from the controller 560.

The controller 560 may receive data from a distance measurement device565. The distance measurement device may provide data indicating thedistance to a nearest foreground object and/or the distance to afurthest background object. The distance measuring device 565 may be assimple as a tape measure or other manual measuring device used by anoperator who then provides the distance data to the controller using akeyboard or other data entry device (not shown). The distance measuringdevice 565 may be a laser range finder, an acoustic rangefinder, anoptical rangefinder, or other range finding device that may interfacewith the controller 560 via a dedicated connection or via a network.

The distance measuring device 565 may not be a separate device, but maybe the camera platform 550 operating under control of an operator and/orthe controller 560. To measure distance, the convergence angle betweenthe cameras 510L, 510R may be adjusted, automatically or under controlof an operator, such that the images captured by the cameras 510L, 510Rconverge at a foreground object or a background object. The convergencedistance to the foreground or background object may then be calculatedfrom the interocular distance and convergence angle between the cameras510L and 510R using the formulas given above. To provide maximumaccuracy when the camera platform is used to measure distance, theinterocular distance may be temporarily set to a maximum value.

The controller 560 may be coupled to an operator interface 562. Thecontroller 560 may receive data from the operator interface 562indicating a focus-convergence offset, as described above. Thecontroller 560 may receive data from the operator interface 562indicating a maximum allowable disparity. The controller 560 may alsoreceive data from the operator interface 562 indicating the focusdistance and focal length of the lenses 512L, 512R.

The operator interface 562 may be partially or wholly incorporated intothe camera platform 550. The operator interface 562 may be close to thecamera platform 550 or partially or wholly remote from the cameraplatform 550. For example, the focus mechanism 556 and/or the zoommechanism 558 may be manually controlled by one or more operators suchas a cameraman and/or an assistant cameraman. In this case, the focusmechanism 556 and/or the zoom mechanism 558 may provide data to thecontroller 560 indicating the manually-set focus distance and/or focallength. Similarly, control actuators to set the focus-convergence offsetand/or the maximum allowable disparity may be located on the cameraplatform for operation by the cameraman and/or the assistant cameraman.

The operator interface 562 may be partially or wholly incorporated intothe controller 560. For example, in situations where thefocus-convergence offset and/or the maximum allowable disparity arefixed during the recording of a scene, the focus convergence offsetand/or the maximum allowable disparity may be manually provided to thecontroller using a keyboard or other data entry device. In situationswhere one or both of the focus-convergence offset and/or the maximumallowable disparity will be varied during the recording of a scene, thefocus-convergence offset and/or the maximum allowable disparity may becontrolled using, for example, arrows keys on a keyboard or one or morecontinuous control devices such as a potentiometer, joystick or mouse.

The controller 560 may interface with the camera platform 550. Thecontroller 560 may be integrated into the camera platform 550. Thecontroller may provide data to and/or receive data from the focusmechanism 556 and the zoom mechanism 558 indicating the focus distanceand focal length, respectively, of the lenses 512L, 512R. The controller560 may provide data to the IOD mechanism 552 and the Θ mechanism 554 toset the interocular distance and the convergence angle, respectively,between the cameras 510L, 510R. The controller 560 may provide data tothe IOD mechanism 552 and the Θ mechanism 554 based on the focusdistance and focal length of the lenses 512L, 512R, thefocus-convergence offset, the maximum allowable disparity, and thedistance to the nearest foreground object and/or the distance to thefurthest background object. The controller 560 may provide data to theIOD mechanism 552 to set the interocular distance such that the largestdisparity in the recorded image does not exceed the maximum allowabledisparity value.

The controller 560 may be coupled to the camera platform 550 and theoperator interface 562 via a network which may be a local area network;via one or more buses such as a USB bus, a PCI bus, a PCI Express bus,or other parallel or serial data bus; or via one or more direct wired orwireless connections. The controller 560 may be coupled to the cameraplatform 550 and the operator interface 562 via a combination of one ormore of direct connections, network connections, and bus connections.

FIG. 6 is a block diagram of a computing device 660 that may be suitablefor the controller 560. As used herein, a computing device refers to anydevice with a processor, memory and a storage device that may executeinstructions including, but not limited to, personal computers, servercomputers, computing tablets, set top boxes, video game systems,personal video recorders, telephones, personal digital assistants(PDAs), portable computers, and laptop computers. The computing device660 may include hardware, firmware, and/or software adapted to performthe processes subsequently described herein. The computing device mayinclude a processor 664 coupled to memory 666 and a storage device 668.

The storage device 668 may store instructions which, when executed bythe computing device 660, cause the computing device to provide thefeatures and functionality of the controller 560. As used herein, astorage device is a device that allows for reading from and/or writingto a storage medium. Storage devices include hard disk drives, DVDdrives, flash memory devices, and others. Each storage device may accepta storage media. These storage media include, for example, magneticmedia such as hard disks, floppy disks and tape; optical media such ascompact disks (CD-ROM and CD-RW) and digital versatile disks (DVD andDVD±RW); flash memory cards; and other storage media. The metadatalibrary 190 may also include a storage server (not shown) or othercomputing devices.

The computing device 660 may include or interface with a display device670 and one or more input devices such a keyboard 672. The computingdevice 660 may also include a network interface unit 674 to interfacewith one or more networks 676. The network interface unit 674 mayinterface with the network 676 via a wired or wireless connection. Thenetwork 676 may be the Internet or any other private or public network.

The computing device 660 may receive distance data from a distancemeasuring device 665. The computing device 660 may be coupled to thedistance measuring device 665 by a dedicated wired or wirelessconnection or via a network. The computing device 660 may receivedistance data from the distance measuring device 665 via an operator(not shown) who may enter the distance data using an input device suchas the keyboard 672.

The computing device 660 may also include a camera interface unit 678 tointerface with a camera platform 650, and/or a camera operator interface662. The camera interface unit 678 may include a combination ofcircuits, firmware, and software to interface with the camera platform650, and/or the camera operator interface 662. The camera interface unit678 may be coupled to the camera platform 650, and/or the cameraoperator interface 662 via a network which may be a local area network;via one or more buses such as a USB bus, a PCI bus, a PCI Express bus,or other parallel or serial data bus; or via one or more direct wired orwireless connections. The camera interface unit 678 may be coupled tothe camera platform 650, and/or the camera operator interface 662 via acombination of one or more of direct connections, network connections,and bus connections.

The processes, functionality and features of the computing device 660may be embodied in whole or in part in software which may be in the formof firmware, an application program, an applet (e.g., a Java applet), abrowser plug-in, a COM object, a dynamic linked library (DLL), a script,one or more subroutines, or an operating system component or service.The computing device 660 may run one or more software programs aspreviously described and may run an operating system, including, forexample, versions of the Linux, Unix, MS-DOS, Microsoft Windows, PalmOS, Solaris, Symbian, and Apple Mac OS X operating systems. The hardwareand software and their functions may be distributed such that somefunctions are performed by the processor 664 and others by otherdevices.

Description of Processes

FIG. 7 is a flow chart of an exemplary process 780 for recordingstereographic images using a stereographic camera system such as thestereographic camera 500. Specifically, FIG. 7 is a flow chart of aprocess for recording a scene without foreground objects, such as thescene 105. The flow chart has both a start 782 and an end 798 for anysingle scene, but the process 780 is continuous in nature and theactions within the process may be performed continuously and innear-real time during the recording of the scene. Additionally, theprocess 780 may be repeated for each scene that is recorded.

Within this patent, the phrase “near-real time” means in real timeexcept for processing delays that are very short compared with temporalevents in the scene being recorded.

At 784, an extreme object distance (EOD), or the distance to an objectwithin the scene that is the furthest from the stereographic camera, maybe determined. The EOD may be determined by a tape measure or othermanual measuring device used by an operator who then enters the distancedata into the stereographic camera system using a keyboard or other dataentry device. The EOD may be determined by a laser range finder, anacoustic rangefinder, an optical rangefinder, or other range findingdevice that may interface with the stereographic camera system via adedicated connection or via a network. The EOD may be determined usingthe stereographic camera system itself as a range finding device, aspreviously described.

When recording scenes where the stereographic camera remains fixed withrespect the background, the EOD may be determined once prior to thestart of recording. The EOD may then be considered as a constant duringthe recording period in which the scene is recorded.

When recording scenes where the stereographic camera and the backgroundmove with respect to each other during the recording period, the EOD maybe determined continuously and in real-time using a laser range finder,optical range finder, acoustic range finder, or other range-findingapparatus coupled to the stereographic camera.

At 786, the stereographic camera system may receive inputs indicating amaximum allowable disparity, a focal distance-convergence distanceoffset, a focus distance of lenses in the stereographic camera, and afocal length or zoom value of the lenses. The maximum allowabledisparity, the focal distance-convergence distance offset, a focusdistance, and the focal length may be set by one or more operators suchas a cameraman, assistant cameraman, or director. The focal length maycommonly be set by an operator such as the assistant cameraman. However,the distance to a primary scene object may be measured in real timeusing a laser, acoustic, optical, or other range-finding device. Thefocal length may be automatically set in response to the real-timemeasurement such that the camera lenses are focused on the primary sceneobject.

The inputs indicating the maximum allowable disparity, the focaldistance-convergence distance offset, the focus distance and the focallength may be received in the form of manually-entered data, analog ordigital signals, or data received via a network.

At 788, the convergence distance CD may be calculated based on the focusdistance and the focus distance-convergence distance offset inputs. Theconvergence distance may be calculated using either formula (3) orformula (4) as described above.

At 790, an interocular distance IOD may be calculated and set. The IODmay be calculated based on the extreme object distance as determined at784, the maximum allowable disparity input and focal length inputreceived at 786, and the convergence distance calculated at 788. The IODmay be calculated using the formulaIOD=[Arctangent(W/FL)×EOD×CD×MD×2]/(EOD−CD)  (7)

-   -   wherein IOD=the interocular distance        -   W=a width of an image sensor within each camera        -   FL=the focal length of the lenses        -   EOD=the extreme object distance        -   MD=the maximum disparity as a fraction of the width of the            scene recorded by the stereographic camera        -   CD=the convergence distance.

At 792, the convergence angle Θ may be calculated and set. Theconvergence angle Θ may be calculated from the convergence distance CDand the interocular distance IOC using formula (1) as described above.

The convergence distance CD, the interocular distance IOD, and theconvergence angle Θ may be calculated by a controller, such as thecontroller 560, which may be a computing device such as the computingdevice 660. The IOD and the convergence angle Θ may be set by a cameraplatform, such as the camera platform 550, in response to data providedby the controller.

At 794, a determination may be made if the recording of the scene hasbeen completed. If the recording is ongoing, the process 780 may repeatcontinuously and in near real-time from 786 if the MOD is constantduring the scene. The process 780 may repeat continuously and in nearreal-time from 784 (as indicated by the dashed line) if the MOD variesduring the scene. When the recording of a scene has been completed, theprocess 780 may finish at 798. Subsequently, the process 780 may startagain from 782 to record the next scene.

CLOSING COMMENTS

Throughout this description, the embodiments and examples shown shouldbe considered as exemplars, rather than limitations on the apparatus andprocedures disclosed or claimed. Although many of the examples presentedherein involve specific combinations of method acts or system elements,it should be understood that those acts and those elements may becombined in other ways to accomplish the same objectives. With regard toflowcharts, additional and fewer steps may be taken, and the steps asshown may be combined or further refined to achieve the methodsdescribed herein. Acts, elements and features discussed only inconnection with one embodiment are not intended to be excluded from asimilar role in other embodiments.

For means-plus-function limitations recited in the claims, the means arenot intended to be limited to the means disclosed herein for performingthe recited function, but are intended to cover in scope any means,known now or later developed, for performing the recited function.

As used herein, “plurality” means two or more.

As used herein, a “set” of items may include one or more of such items.

As used herein, whether in the written description or the claims, theterms “comprising”, “including”, “carrying”, “having”, “containing”,“involving”, and the like are to be understood to be open-ended, i.e.,to mean including but not limited to. Only the transitional phrases“consisting of” and “consisting essentially of”, respectively, areclosed or semi-closed transitional phrases with respect to claims.

Use of ordinal terms such as “first”, “second”, “third”, etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

As used herein, “and/or” means that the listed items are alternatives,but the alternatives also include any combination of the listed items.

It is claimed:
 1. A stereographic camera system, comprising: a leftcamera and a right camera including respective lenses plural mechanismsto synchronously set a focal length of the lenses, to synchronously seta focus distance of the lenses, to set a convergence angle between theleft and right cameras, and to set an intraocular distance between theleft and right cameras a distance measuring device to measure an extremeobject distance a controller comprising circuits and software to performactions comprising receiving inputs indicating a maximum allowabledisparity, the focal length of the lenses, and the focus distance of thelenses causing the intraocular distance to be set to a value calculatedfrom the extreme object distance, the maximum allowable disparity, thefocal length, and a convergence distance causing the convergence angleto be set to a value calculated from the intraocular distance and theconvergence distance.
 2. The stereographic camera system of claim 1,wherein the actions performed by the controller are performedcontinuously in near-real time.
 3. The stereographic camera system ofclaim 1, wherein the interocular distance is calculated using theformulaIOD=[Arctangent(W/FL)×EOD×MD×2]/(EOD−CD) wherein IOD=the interoculardistance W=a width of an image sensor within each camera FL=the focallength of the lenses EOD=the extreme object distance MD=the maximumdisparity as a fraction of the width of the scene recorded by thestereographic camera CD=the convergence distance.
 4. The stereographiccamera system of claim 1, wherein the convergence distance CD distanceis calculated from the focus distance FD using a formula selected fromCD=FD, CD=FD+α, and CD=FD(1+β), wherein α and β are operator-definedvalues.
 5. A method for controlling a stereographic camera, comprising:determining an extreme object distance receiving inputs indicating amaximum allowable disparity, a focal length of left and right lensesassociated with left and right cameras, and a focus distance of thelenses causing an intraocular distance between the left and rightcameras to be set to a value calculated from the extreme objectdistance, the maximum allowable disparity, the focal length, and aconvergence distance causing the convergence angle between the left andright cameras to be set to a value calculated from the intraoculardistance and the convergence distance.
 6. The method for controlling astereographic camera of claim 5, wherein the method is performedcontinuously in near-real time.
 7. The method for controlling astereographic camera of claim 5, wherein the interocular distance iscalculated using the formulaIOD=[Arctangent(W/FL)×EOD×MD×2]/(EOD−CD) wherein IOD=the interoculardistance W=a width of an image sensor within each camera FL=the focallength of the lenses EOD=the extreme object distance MD=the maximumdisparity as a fraction of the width of the scene recorded by thestereographic camera CD=the convergence distance.
 8. The method forcontrolling a stereographic camera of claim 5, wherein the convergencedistance CD is calculated from the focus distance FD using a formulaselected from CD=FD, CD=FD+α, and CD=FD(1+β), wherein α and β arepredetermined constants.
 9. The method for controlling a stereographiccamera of claim 5, wherein the interocular distance is varied during therecording of a scene.
 10. The method for controlling a stereographiccamera of claim 9, wherein at least one of the focus distance and thefocal length are varied during the recording of the scene.
 11. Themethod for controlling a stereographic camera of claim 9, wherein themaximum disparity is varied during the recording of the scene.
 12. Themethod for controlling a stereographic camera of claim 5, wherein theinputs indicating the maximum allowable disparity, the focal length, andthe focus distance are received from an operator interface.
 13. Acomputing device to control a stereographic camera, the computing devicecomprising: a processor a memory coupled with the processor a storagemedium having instructions stored thereon which when executed cause thecomputing device to perform actions comprising receiving inputsindicating an extreme object distance, a maximum allowable disparity, afocal length of lenses associated with a left camera and a right camera,and a focus distance of the lenses outputting data defining aninterocular distance between the left camera and the right camera, theinterocular distance calculated from the extreme object distance, themaximum allowable disparity, the focal length, and a convergencedistance outputting data defining a convergence angle between the leftcamera and the right camera, the convergence angle calculated from theintraocular distance and the convergence distance.
 14. The computingdevice to control a stereographic camera of claim 13, wherein theactions performed by the computing device are performed continuously inreal time.
 15. The computing device to control a stereographic camera ofclaim 13, wherein the interocular distance is calculated using theformulaIOD=[Arctangent(W/FL)×EOD×MD×2]/(EOD−CD) wherein IOD=the interoculardistance W=a width of an image sensor within each camera FL=the focallength of the lenses EOD=the extreme object distance MD=the maximumdisparity as a fraction of the width of the scene recorded by thestereographic camera CD=the convergence distance.
 16. The computingdevice to control a stereographic camera of claim 13, wherein theconvergence distance CD distance is calculated from the focus distanceFD using a formula selected from CD=FD, CD=FD+α, and CD=FD(1+β), whereinα and β are operator-defined values.